Help with Loop (C++/MFC)

EOTF · 10-16-2007, 06:04 PM

Hi folks,

I'm having problems with my loops, and possibly more...hehe!

I'm loading a text file, which has 1 word per line, into a buffer and I want to search the buffer for all the words that start with the same prefix (3 letters) and return the words in an edit box.

I successfully accomplished reading 1 line, compare the prefix, and show the word in an edit box if prefix matches. Now, I'm just stuck with making it loop.

Exemple:
The Prefix is: "Bla".
The text file contains:
Benji
Bennett
Bentley
Beverly
Billy
Birch Grove
Birch Hill
Birch
Birchdale
Birchmount
Birchwood
Black Beach
Black
Blair
Bleury
Blue Heron
Blue Rock

The program will return:
Black Beach
Black
Blair

Here's the code for the button:

Quote:

#include <iostream>
#include <fstream>
#include <strstream>

//....

void Csn3Dlg::OnBnClickedButton1()
{
UpdateData(TRUE);

FILE * pFile;
char buffer [20];
CString prefix = "Old";
CString readprefix;
CString temp;
CString read;
int count=0;

pFile = fopen ("d:\\namelist.txt" , "r");

if (pFile == NULL)
{
MessageBox("Error opening file", NULL, MB_OK | MB_ICONSTOP);
exit(0);
}

else
{
while ( ! feof (pFile) )
{
fgets (buffer , 20 , pFile);
fputs (buffer , stdout);
read = read+buffer+"\r\n";
}
fclose (pFile);

//My problems are in there:
while ( prefix != readprefix )
{
for (int j = count ; read[j]!='\n'; j++)
temp = temp+read[j];
for(int i=0 ; i!=3 ; i++)
readprefix = readprefix+temp[i];

if(prefix == readprefix)
break;
else
count++;
}

m_out = temp;

}

UpdateData(FALSE);
}

Any suggestions or help will be much appreciated!

Hivemind · 10-17-2007, 09:34 AM

It would probably be a better idea to ask that question here instead. Or, if you prefer Microsofts web interface go here (it's the same group).

Wim Sturkenboom · 10-17-2007, 10:34 AM

@Hivemind
Why? It's a fully valid C++ problem that any C++ programmer should be able to advise on.

@EOTF
Unfortunately I don't do OOP, so can not really advise. A thing that looks suspicious (from a C perspective) is that you add read and buffer together. Not sure if that's possible in C++ as they are of different types (Cstring and char).

Further I suggest that you look at string functions for compare and substring etc (e.g. here.

Hivemind · 10-17-2007, 10:47 AM

Well, just because this happens to be a class member function doesn't make it an oop-problem. I noticed the OP is using UpdateData(), which should be avoided, and the experts who can point out and explain such things to him usually can be found there, not here. And if he's using UpdateData() there are likely to be all sorts of things he does in MFC which can be done in a better way. I rarely see MFC questions here. I don't see what your contribution was, I didn't answer his question but pointed him to a place where his question most likely wouldn't go unanswered for so long as it did here. Maybe you just don't like the fact that I pointed the OP to another place?

Hivemind · 10-17-2007, 11:14 AM

The question really had nothing to do with MFC, as was pointed out, but I still think it's a good idea if the OP visits a really good MFC forum, like the ones I suggested earlier. A standard c++ solution to the problem I provide here, I wrote it from scratch, not bothering with the OPs attempt.

Code:

#include <fstream>
#include <iostream>
#include <string>

using namespace std;

bool matches_prefix(const string& word, const string& prefix);

int
main()
{
   ifstream infile("words.txt");

   if (!infile)
   {
      cerr << "Error opening file." << endl;

      return 1;
   }

   const string prefix = "Bla";
   string current_word;

   while (getline(infile, current_word))
   {
      if (matches_prefix(current_word, prefix))
      {
         cout << current_word << endl;
      }
   }
}

bool
matches_prefix(const string& word, const string& prefix)
{
   if (word.length() < prefix.length())
   {
      return false;
   }

   string s = word.substr(0, prefix.length());

   return s == prefix;
}

Tried with the example file showed by the OP and got the expected output.

EOTF · 10-18-2007, 01:11 PM

Hi again,

First of, Hivemind, thanks for the code pal, it's working great! It's not MFC, but I found a way around it by exporting the result into a text file, than read the text file from the MFC app. I'll use that until I figure out how to do it properly in an MFC app.

Second, I'm sorry for posting in the wrong group...it is my first post in this Forum!

And finally, I'm using MFC because I love it and this is how I want the result to display; in an Edit Box, not in a DOS window. This is just a small part of a bigger program (MFC) and the prefix part was the only part that's been giving me a bit of a hard time.

Thanks again folks!